Archive of Mechanical Engineering

In the presented work, the author describes a new diagnostic method of ballistic resistance of multi– layered shields. The proper ballistic energy absorbed by the shield is introduced in the form V²_BL[R] according to Recht’s and Ipson’s method, and V²_BL[Z] according to author’s method. The kinetic energy of the bullet m_p · V²_p/2 and the momentum of force I are transferred to the shield and the dynamometer of ballistic pendulum. They are used to determine the proper energy V²_BL[Z] and ballistic thickness h_BL of the shield. The procedure can be widened onto the absorption of the energy by individual layers of the shield, where: A^Hn_an,bn – the effect of n – interlayer on proper energy absorbed by the shield. The effectiveness of the used methods is expressed by average effectiveness coefficient β_s of proper energy absorbed by the shield V²_BL as well as by average mass coefficients α²_s . The ballistic shields can be composed of different grades of metal layers and interlayer areas with well-chosen ballistic proprieties.

The maximization of interlayer effectiveness N_n[R] and N_n[Z] as well as relative mass effectiveness M_s[R] and M_s[Z] leads to optimum conditions of selection of multi–layered shields structures.

In the paper, the authors describe and solve the problem of optimum control of selected vibration forms in mechanical systems. Two illustrative examples have been used to present the procedure for determination of the optimum controller coefficients.

In the first example, a simplified mechanical system is considered, while in the second one – a rotor with magnetic bearing. In both cases, the integral performance indices have been defined in order to minimize the vibration level at selected points of the structures.

The system with the magnetic bearing is structurally unstable. For this reason, the authors present the way of finding the weight coefficients of integral performance index for unstable, multi-degrees-of-freedom system. In that way, the selected modal forms attain the previously assumed dynamic properties and the performance index takes the minimum value. The results of numerical analysis show that the proposed way is efficient and makes it possible to control selected forms of vibration in the system.

The paper presents theoretical analysis and simulation results of the process of regular surface texture generation by grinding with the wheel shaped in a special way. Simple variant of the method consists in grinding with the wheel having single helical groove. Non-uniform load of abrasive grains located in different zones of the wheel circumference was described. Two models (deterministic and probabilistic) of the wheel active surface were developed, assuming different grain arrangement. Results of two models were compared and differences were explained.

Results of mathematical modelling and computer simulation of transient processes in the turbine jet engine SO-3 have been presented. The transient processes result from two different fault conditions. In the first case, the transient process has been induced with a rapid fuel shut-off. In the second case, the transient process follows some failure to the shaft that connects the turbine rotor to that of the compressor. The failure occurred in the area of the middle engine bearing support.

This study presents a description of the mechanics of forming dough pieces into cylindrical (cylinder-like) shapes. Based on the configuration of forming, the movement of the formed piece and its surface deformations were described. Kinematic relationships concerning the dough piece material as a rheological fluid were formulated. Next, the relationships coupling the kinematic quantities present with both descriptions were determined. The components of the deformation rate tensor, presented in the assumed forming configuration (cylindrical coordinate system), describe the velocity distribution on the surface of dough piece being formed and deformed. The determined kinematic quantities and their interrelations may be used to describe the process of forming dough pieces into cylindrical shapes.